Human Mercury Biomonitoring Under the Minamata Convention: Blood, Urine, Hair, and Tissue Biomarkers (2000-2026)

Mercury (Hg) is a globally ubiquitous environmental pollutant classified by the World Health Organization among the chemicals of major public health concern. It occurs as elemental mercury, inorganic mercury, and organic mercury, each with distinct toxicokinetics and target organs. Human exposure arises mainly from fish and seafood consumption. Additional important sources include dental amalgam restorations, occupational settings, mercury-containing skin-lightening cosmetics, artisanal and small-scale gold mining (ASGM), and environmental remobilization of Hg naturally stored in soils and sediments through erosion, flooding dynamics, biomass burning, and soil mobility processes, especially in tropical regions such as the Amazon Basin. This is a narrative review of the scientific literature published from January 1, 2000 to June 15, 2026 on Hg concentrations measured in human blood and other biological tissues. Background blood Hg concentrations in general populations are commonly below 1-3 µg/L, while values exceeding 5 µg/L are uncommon in unexposed populations and may approach biomonitoring guidance thresholds. NHANES data show a progressive decline in blood Hg among women of reproductive age. Markedly elevated levels are consistently reported in high-fish-consuming coastal and Arctic Indigenous communities, ASGM workers, users of mercury-containing skin-lightening products, and individuals with extensive amalgam restorations. Mercury accumulates in the kidney cortex (inorganic Hg) and brain (inorganic and organic forms), with concentrations that may persist long after exposure cessation. Cardiovascular and renal effects of chronic Hg exposure are increasingly documented, complementing neurotoxicological evidence that remains most firmly established at high-level exposures, such as Minamata disease and occupational poisoning, whereas associations reported at typical environmental exposure levels are largely statistical rather than indicative of overt clinical neurotoxicity. A recurring pattern across the reviewed literature is that biomarker concentrations and temporal trends differ markedly between high-income and low- and middle-income countries, with declining exposure and denser monitoring coverage in the former contrasting with persistently elevated levels and sparse surveillance data in the latter, a gap directly relevant to evaluating the effectiveness of the Minamata Convention under its Article 22. Continued biomonitoring, strict regulatory enforcement, and full implementation of the Minamata Convention are essential to protect vulnerable populations worldwide.